Optical constants of SCHOTT - multiple purpose
B 270® Superwite
(0.43583 – 0.65627)
Other optical constants
20 °C. Clear high transmission crown glass (modified soda-lime glass) available in form of sheets, profile rods strips and blanks
B 270 datasheet, August 1993
More info - wiki
SCHOTT AG is a German glass manufacturer. SCHOTT also publishes a glass catalog (SCHOTT Optical Glass Datasheets), which is a standard reference for the properties of many optical glasses.